1. Field of the Invention
The present invention generally relates to an electromagnetic pointer control method, and more particularly to an electromagnetic pointer control method which can provide an electromagnetic pointer with a tip pressure-sensitive function.
2. Description of Related Art
The operation principle of electromagnetic type input technology is performed by a circuit board with a plurality of antennas or sensor coils arranged along axial directions and an electromagnetic pen which can emit electromagnetic signals. The sensing plane of an electromagnetic input apparatus includes a plurality of antennas or sensor coils. The antennas or sensor coils are arranged under a work surface or a display panel of the electromagnetic input apparatus. The coordinates of the electromagnetic pen are obtained through the transmitting and receiving of electromagnetic waves between the circuit of the electromagnetic pen and the antennas or the sensor cons.
The circuit of the electromagnetic pen usually comprises an inductor, a capacitor and relative components enclosed in a case. The inductor constituted by a ferrite core winded with a metal coil and the capacitor constitute the circuit to transmit and receive electromagnetic signals with the antennas or sensor coils. The frequency of the circuit is determined according to the capacitance and the inductance connected in parallel. When a user utilizes the electromagnetic pen to perform writing function on the input apparatus, the tip of the electromagnetic pen being pressed would induce the continuous changes of the inductance or capacitance as well as the frequency of the circuit. The input apparatus detects and calculates the frequency of the electromagnetic signals received to obtain pressure levels of the electromagnetic pen via an internal circuit.
The main design principle for obtaining pressure gradient value of an electromagnetic pen mentioned above is to continuously change capacitance or inductance so as to alter the transmitting frequency of the oscillation circuit when the pen tip is pressed, so that a trigger structure connected to the pen tip which can change the capacitance or inductance is necessary.
The invention focuses on an electromagnetic control method which can be used on an electromagnetic pen without a trigger structure connected to the pen tip so that any electromagnetic pen without a trigger structure can have a tip pressure-sensitive function.